The Calgary lawyer is also the subject of an investigation by Alberta's Chief Electoral Officer. It's alleged he raised money outside the province for his senate race.

He released a statement Friday afternoon that he's resigning his community involvements as he's now a senator-in-waiting.

The Canadian Taxpayers Federation raised concerns last month about expenses claimed by Doug Black while he chaired the University of Calgary's board of governors. (dougblack.ca)

In the letter, Black states he has paid back all expenses he incurred while serving as board chair and that he has learned a valuable lesson.

The interim chair of the board, current vice-chair Bonnie DuPont, said Friday they knew once Black won a senator-in-waiting spot in last spring's election, that he would be leaving this fall.

"He's resigned effective immediately," said DuPont.

Expenses claimed by Black include:

$508.95 per night at the Four Seasons in Houston

$2,200.78 for a board dinner at the Ranchmen's Club, including $550 for wine

$358.04 for one night at the Four Seasons Hotel in Vancouver

$112.45 for dinner for Black and U of C president Elizabeth Cannon at Il Sogno on April 4, 2011

$120 for a private driver to transport Black to and from dinner with Cannon at Il Sogno on April 4, 2011

"He’s done a great job. He's been a very good chair for the last 18 months and before that served as a board member and we thank him for his service."

In September, university president Elizabeth Cannon said mistakes were made and said oversight of such claims would be fixed.

"We are fixing those and looking how we can strengthen the oversight ... and ensure that those kinds of mistakes don't get made in the future," she said then.

In a news release at the time, the university claimed Black’s improper expense claims were uncovered by a quarterly review of the chairman’s expenses in June. It found the "error" made by Black in claiming first-class flights and Black "promptly" cut the university a cheque for nearly $5,400.

Scott Hennig of the Canadian Taxpayers Federation said he's happy that the money will be paid back.

Hennig said he was skeptical on the issue of whether Black stepped down because of his senator-in-waiting-role.

"There's not much you have to do to become a senator, to prepare. Not like he's going to go through some sort of boot camp which will eat up all of his time," said Hennig.

"There's no question this has everything to do with the expense issue."